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User Guide
OpenEdge Replication and after-imaging : The role of after-image extents in the Replication process : After-image extent sizing on a source database

After-image extent sizing on a source database

After you estimate the volume of after-image data your database generates, you can resize the after-image extents for use with OpenEdge Replication. Progress Software Corporation recommends that the size of one after-image extent be capable of storing four hours of typical database activity when running OpenEdge Replication. Additionally, Progress Software Corporation further recommends that the total size of all after-image extents be enough to store one week of typical database activity.
These recommendations are based on the following:
*The total capacity of your source database after-image extents must include additional capacity to allow for some target database downtime.
*Most simple hardware failures can be resolved within a four-hour period. For example, if a drive controller or network card fails, it is a simple operation to have another installed.
*In certain situations, it may be necessary to have your target machine out of service for an extended length of time. The total after-image storage allocated must have the capacity to store large numbers of transaction log records.
There are additional transaction log records written by a database that is enabled as a source database. These additional transaction log records require more after-image space, referred to as replication overhead. In order to calculate the replication overhead, the estimated after-image size information (obtained in The role of after-image extents in the Replication process) must be multiplied by 1.5.